1. Field of the Invention
The present invention relates to an image pickup apparatus.
2. Description of the Related Art
Widely used image pickup apparatuses such as a digital still camera or a video camera have a lens whose focal length is changed in accordance with the distance between lens and subject and the angle of view, and which uses a zoom capability of zooming the subject image by using the lens. The zoom capability is roughly classified into optical and electronic zoom capabilities. In the optical zoom capability, the subject image is zoomed by mechanically moving the lens provided in the image pickup apparatus. In the electronic zoom capability, an image output from an image sensor is processed such that appropriate pixels are interpolated into pixels constituting the image, or pixels are thinned out therefrom, thereby enlarging or reducing the subject image. In such a manner, the electronic zoom capability does not need a driving mechanism for the lens. Accordingly, the image pickup apparatus having the electronic zoom capability can be formed compactly at low cost, but provides an image with a low quality, as compared with the image pickup apparatus having the optical zoom capability.
As shown in FIG. 10, Jpn. Pat. Appln. KOKAI Publication No. 10-233950 discloses an image input optical system 901 having a function of squeezing a peripheral part of an input image, and a light-reception device 902 which receives light transmitted through the image input optical system 901 to form a subject image, and has pixels arranged at a uniform density. The subject image is corrected, since it is distorted through the image input optical system 901. By virtue of the above feature, even with the electronic zoom capability, the invention of the publication can form an image whose center part is equivalent in quality to that of an image obtained with the optical zoom capability. However, in the method of the publication, when images are formed by using a wide-angle lens or a telephoto lens, although their center parts are not low in quality, their peripheral parts are low in quality.